start a dissector for GDB's remote serial protocol

Change-Id: I8e20917ac08e2349caf330ee967d24d7c738bb71
Reviewed-on: https://code.wireshark.org/review/1815
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>
Tested-by: Martin Kaiser <wireshark@kaiser.cx>

3 files changed, 264 insertions, 0 deletions

diff --git a/epan/CMakeLists.txt b/epan/CMakeLists.txt
index 16a691293b..b783831c40 100644
--- a/epan/CMakeLists.txt
+++ b/epan/CMakeLists.txt
@@ -677,6 +677,7 @@ set(DISSECTOR_SRC
 	dissectors/packet-fw1.c
 	dissectors/packet-g723.c
 	dissectors/packet-gadu-gadu.c
+	dissectors/packet-gdb.c
 	dissectors/packet-gdsdb.c
 	dissectors/packet-gearman.c
 	dissectors/packet-ged125.c
diff --git a/epan/dissectors/Makefile.common b/epan/dissectors/Makefile.common
index e353bfc24d..f5026104d2 100644
--- a/epan/dissectors/Makefile.common
+++ b/epan/dissectors/Makefile.common
@@ -597,6 +597,7 @@ DISSECTOR_SRC = \
 	packet-fw1.c		\
 	packet-g723.c		\
 	packet-gadu-gadu.c	\
+	packet-gdb.c		\
 	packet-gdsdb.c		\
 	packet-gearman.c	\
 	packet-ged125.c		\
diff --git a/epan/dissectors/packet-gdb.c b/epan/dissectors/packet-gdb.c
new file mode 100644
index 0000000000..23b1355ac9
--- /dev/null
+++ b/epan/dissectors/packet-gdb.c
@@ -0,0 +1,262 @@
+/* packet-gdb.c
+ * Routines for dissection of GDB's Remote Serial Protocol
+ *
+ * Copyright 2014, Martin Kaiser <martin@kaiser.cx>
+ *
+ * Wireshark - Network traffic analyzer
+ * By Gerald Combs <gerald@wireshark.org>
+ * Copyright 1998 Gerald Combs
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/*
+ * The GDB Remote Serial Protocol is used between an instance of the
+ * GNU Debugger and a remote target such as an embedded system.
+ * It can be run over TCP/IP or a serial line, we support only TCP/IP.
+ *
+ * The protocol specification is in Annex E of the GDB user manual
+ * http://www.gnu.org/software/gdb/documentation/
+ *
+ */
+
+#include "config.h"
+
+#include <ctype.h>
+
+#include <glib.h>
+#include <epan/expert.h>
+#include <epan/packet.h>
+#include <epan/tvbparse.h>
+
+enum {
+    GDB_TOK_ACK,
+    GDB_TOK_START,
+    GDB_TOK_PAYLOAD,
+    GDB_TOK_END,
+    GDB_TOK_CHKSUM
+};
+
+static const value_string gdb_ack[] = {
+    { '+', "Transmission successful" },
+    { '-', "Transmission failed" },
+    { 0, NULL }
+};
+
+
+void proto_register_gdb(void);
+
+static int proto_gdb = -1;
+
+static gint ett_gdb = -1;
+
+static int hf_gdb_ack = -1;
+static int hf_gdb_start = -1;
+static int hf_gdb_payload = -1;
+static int hf_gdb_end = -1;
+static int hf_gdb_chksum = -1;
+
+static tvbparse_wanted_t *want;
+
+static void
+dissect_gdb_token(void *tvbparse_data, const void *wanted_data, tvbparse_elem_t *tok)
+{
+    proto_tree *tree;
+    guint       token;
+    guint8      ack;
+
+    if (!tok)   /* XXX - is this check necessary? */
+        return;
+
+    tree = (proto_tree *)tvbparse_data;
+    token = GPOINTER_TO_UINT(wanted_data);
+
+    /* XXX - check that tok->len is what we expect? */
+    switch (token) {
+        case GDB_TOK_ACK:
+            ack = tvb_get_guint8(tok->tvb, tok->offset);
+            proto_tree_add_uint_format(tree, hf_gdb_ack,
+                    tok->tvb, tok->offset, tok->len, ack,
+                    "Acknowledgement: %s (%c)",
+                    val_to_str_const(ack, gdb_ack, "unknown"), ack);
+            break;
+        case GDB_TOK_START:
+            proto_tree_add_item(tree, hf_gdb_start,
+                    tok->tvb, tok->offset, tok->len, ENC_ASCII|ENC_NA);
+            break;
+        case GDB_TOK_PAYLOAD:
+            proto_tree_add_item(tree, hf_gdb_payload,
+                    tok->tvb, tok->offset, tok->len, ENC_NA);
+            break;
+        case GDB_TOK_END:
+            proto_tree_add_item(tree, hf_gdb_end,
+                    tok->tvb, tok->offset, tok->len, ENC_ASCII|ENC_NA);
+            break;
+        case GDB_TOK_CHKSUM:
+            /* the spec is not really explicit but it seems that the
+               checksum is big endian */
+            proto_tree_add_item(tree, hf_gdb_chksum,
+                    tok->tvb, tok->offset, tok->len, ENC_BIG_ENDIAN);
+            break;
+        default:
+            break;
+    }
+}
+
+static void init_gdb_parser(void) {
+    tvbparse_wanted_t *want_ack;
+    tvbparse_wanted_t *want_start;
+    tvbparse_wanted_t *want_payload;
+    tvbparse_wanted_t *want_end;
+    tvbparse_wanted_t *want_chksum;
+
+    want_ack = tvbparse_chars(-1, 1, 1, "+-",
+            GUINT_TO_POINTER(GDB_TOK_ACK), NULL, dissect_gdb_token);
+    want_start = tvbparse_chars(-1, 1, 1, "$",
+            GUINT_TO_POINTER(GDB_TOK_START), NULL, dissect_gdb_token);
+    want_payload = tvbparse_not_chars(-1, 1, 0, "$#",
+            GUINT_TO_POINTER(GDB_TOK_PAYLOAD), NULL, dissect_gdb_token);
+    want_end = tvbparse_chars(-1, 1, 1, "#",
+            GUINT_TO_POINTER(GDB_TOK_END), NULL, dissect_gdb_token);
+    want_chksum = tvbparse_chars(-1, 2, 2, "0123456789abcdefABCDEF",
+            GUINT_TO_POINTER(GDB_TOK_CHKSUM), NULL, dissect_gdb_token);
+
+    want = tvbparse_set_seq(-1, NULL, NULL, NULL,
+            tvbparse_some(-1, 0, 1, NULL, NULL, NULL, want_ack),
+            want_start, want_payload, want_end, want_chksum, NULL);
+}
+
+
+static void
+dissect_gdb_packet(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)
+{
+    proto_item  *ti;
+    proto_tree  *gdb_tree;
+    tvbparse_t  *tt;
+
+    col_set_str(pinfo->cinfo, COL_PROTOCOL, "GDB");
+    col_clear(pinfo->cinfo, COL_INFO);
+
+    ti = proto_tree_add_protocol_format(tree, proto_gdb,
+            tvb, 0, tvb_reported_length(tvb), "GDB Remote Serial Protocol");
+    gdb_tree = proto_item_add_subtree(ti, ett_gdb);
+
+    /* XXX support multiple sub-trees */
+    tt = tvbparse_init(tvb, 0, -1, (void *)gdb_tree, NULL);
+
+    while(tvbparse_get(tt, want)) {
+        ;
+    }
+}
+
+
+static void
+dissect_gdb_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+{
+    gint      offset=0, offset_start;
+    gint      pos;
+    guint     packet_len;
+    tvbuff_t *packet_tvb;
+
+    while (tvb_captured_length_remaining(tvb, offset) > 0) {
+        packet_tvb = NULL;
+        offset_start = offset;
+        pos = tvb_find_guint8(tvb, offset, -1, '#');
+        if (pos != -1) {
+            offset += pos;
+            offset++; /* skip the hash sign */
+            /* to have a complete packet, we need another two bytes
+               for the checksum */
+            if (tvb_bytes_exist(tvb, offset, 2)) {
+                offset += 2;
+                packet_len = offset-offset_start;
+                packet_tvb = tvb_new_subset(tvb, offset_start,
+                        packet_len, packet_len);
+            }
+        }
+
+        if (packet_tvb)
+            dissect_gdb_packet(tvb, pinfo, tree);
+        else {
+            pinfo->desegment_offset = offset;
+            pinfo->desegment_len = DESEGMENT_ONE_MORE_SEGMENT;
+            return;
+        }
+    }
+}
+
+
+void
+proto_register_gdb(void)
+{
+    static hf_register_info hf[] = {
+        { &hf_gdb_ack,
+          { "Acknowledge", "gdb.ack", FT_UINT8, BASE_HEX,
+              VALS(gdb_ack), 0, NULL, HFILL } },
+        { &hf_gdb_start,
+          { "Start character", "gdb.start", FT_STRING, BASE_NONE,
+              NULL, 0, NULL, HFILL } },
+        { &hf_gdb_payload,
+          { "Payload", "gdb.payload", FT_BYTES, BASE_NONE,
+              NULL, 0, NULL, HFILL } },
+        { &hf_gdb_end,
+          { "Terminating character", "gdb.end", FT_STRING, BASE_NONE,
+              NULL, 0, NULL, HFILL } },
+        { &hf_gdb_chksum,
+            { "Checksum", "gdb.chksum", FT_UINT8, BASE_HEX,
+                NULL, 0, NULL, HFILL } }
+    };
+
+    static gint *ett[] = {
+        &ett_gdb
+    };
+
+
+    proto_gdb = proto_register_protocol(
+            "GDB Remote Serial Protocol", "GDB remote", "gdb");
+
+    proto_register_field_array(proto_gdb, hf, array_length(hf));
+    proto_register_subtree_array(ett, array_length(ett));
+
+    init_gdb_parser();
+}
+
+
+void
+proto_reg_handoff_gdb(void)
+{
+    static gboolean            initialized = FALSE;
+    static dissector_handle_t  gdb_handle;
+
+    if (!initialized) {
+        gdb_handle = create_dissector_handle(dissect_gdb_tcp, proto_gdb);
+        initialized = TRUE;
+    }
+
+    dissector_add_handle("tcp.port", gdb_handle);
+}
+
+/*
+ * Editor modelines  -  http://www.wireshark.org/tools/modelines.html
+ *
+ * Local variables:
+ * c-basic-offset: 4
+ * tab-width: 8
+ * indent-tabs-mode: nil
+ * End:
+ *
+ * vi: set shiftwidth=4 tabstop=8 expandtab:
+ * :indentSize=4:tabSize=8:noTabs=true:
+ */